The primary aim of the proposed study is to test whether Borderline Personality Disorder (BPD) is familial (i.e., whether BPD in probands is associated with BPD in first degree relatives). The second aim of the proposed study is to test whether three component phenotypic personality traits (affective instability, behavioral dyscontrol, and interpersonal instability), are themselves familial. Each of these traits is a potentially relevant disposition for BPD as well as a variety of other psychiatric disorders. Both aims will provide results that will inform our classification system and provide leads for future genetic research. The proposed study will give direct and blinded assessments to 280 probands and 984 first degree relatives (3.5 per proband, 2.7 being direct). The probands will be comprised by 100 with borderline personality disorder (BPD), 80 with major depressive disorder (MOD), and by 100 non-borderline comparison subjects (NBC). The MDD and NBC samples will be demographically matched with the index BPD probands in gender (all female), age, and socio-ethnicity. The overall sampling strategy is intended to be sufficiently broad to assure a range of scores on the phenotypic traits to extend the generalizability of the findings, while also being sufficiently narrow to anchor the design and assure the hypotheses are testable. We propose in Aim I to use a univariate proband predictive logistic regression model to evaluate the familial aggregation of BPD with the presence or absence of BPD in a relative as the outcome and "he presence or absence of BPD in the proband associated with that relative as the predictor. In Aim II we will use a univariate proband predictive linear regression model with the level of a given trait in a relative as the outcome and the level of that trait in the proband as the predictor. We will also use structural equation modeling to examine whether coaggregation of traits can conform to standardized models. Finally, we will use this study's sample to develop a gene bank for future exploration of genetic associations with BPD and its phenotypic traits.